Tetramine compound and organic el device

ABSTRACT

The present invention provides a method for producing a tetramine compound represented by formula (1): 
     
       
         
         
             
             
         
       
     
     wherein R1, R2 and R3, which may be the same or different, each represents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbon atoms, an unsubstituted aryl group or an aryl group substituted with a tertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or 4.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 10/584,140, filed on Jun. 26, 2006, which is a 371 ofPCT/JP04/19755, filed on Dec. 24, 2004, and claims priority to thefollowing application: Japanese Patent Application No. 2003-434432,filed on Dec. 26, 2003.

TECHNICAL FIELD

The present invention relates to an organic EL element which is a lightemitting element having a hole transport layer, a light emitting layerand an electron transport layer and widely utilized as various displays,and which provides high luminance at low applied voltage and is alsoexcellent in stability.

BACKGROUND ART

An organic EL element is a self-luminous element, so that a brighter,clearer display is possible compared to a liquid crystal element.Further, it has useful characteristics such as a wide view angle andhigh-speed responsibility. Accordingly, studies thereon have been madeby many researchers from long ago.

Initially, an organic electroluminescence element using an organicmaterial had been far from a practical level. However, characteristicsthereof have been dramatically improved by a laminated structure elementdeveloped by C. W. Tang et al of Eastman Kodak Co. in 1987, in whichvarious roles are divided to respective materials. They laminated afluorescent material which is stable in the structure of itsvapor-deposited film and can transport electrons, with organic matterwhich can transport holes, and injected both carriers into thefluorescent material, thereby succeeding in emitting light. Thisimproved the luminous efficiency of the organic electroluminescenceelement, resulting in obtaining a high luminance of 1000 cd/m² or moreat a voltage of 10 V or less (for example, see patent document 1 andpatent document 2). Thereafter, studies for improving thecharacteristics were made by many researchers, and at present, theluminous characteristic of a higher luminance of 10000 cd/m² or morehave been obtained concerning light emission for a short period of time.

Patent Document 1: JP-A-8-48656

Patent Document 2: Japanese Patent No. 3194657

At present, the organic EL elements have been put to practical use, andutilized as displays for cell phones, car audios and the like, and ithas been further expected to enlarge the size and to expand the userange. However, there are still many problems required to be solved. Oneof them is heat resistance at the time when they are driven under hightemperature environment. α-NPD which has been widely used as a holetransport material at present has a problem in heat resistance, and theuse thereof under high temperature environment such as a large-sizeddisplay which generates heat upon use or in-vehicle applications whichrequire high durability has been considered to be impossible (forexample, see non-patent document 1). Accordingly, concerning a presentlyemployed general element constitution, it has been said that the heatstability of the element is determined by the heat stability of the holetransport material. This is because the hole transport material mainlycomposed of an organic amine-based material is inevitablydisadvantageous in terms of heat stability, when attention is paid tothe materials of the respective layers used in organic EL elements.Accordingly, improvements of the heat stability of the hole transportmaterial is considered to lead to improvements of the heat stability ofthe element. The general element constitution referred to hereinindicates one as shown in FIG. 1.

Non-Patent Document 1: M&BE, vol. 11, No. 1 (2000)

DISCLOSURE OF THE INVENTION

The present inventors paid attention to the heat stability of the holetransport material, grasped the glass transition point of a compounddeeply concerned with the heat stability of a vapor-deposited film as animportant factor, and made studies on materials. The glass transitionpoint is an upper limit temperature at which a substance can exist in anamorphous state, and an important physical property value thatdetermines the film stability of the vapor-deposited film.Theoretically, it can be said that the higher the glass transitionpoint, the higher the heat stability of the element. Further, givingattention also to a molecular structure, it was tried to connect diaminecompounds through a plurality of phenyl groups, thereby giving a featureto the molecular structure to improve the stability in an amorphousstate.

An object of the invention is to provide an organic EL element having ahole transport layer excellent in luminous stability when driven at ahigh temperature.

Another object of the invention is to provide an excellent compound as amaterial used for the hole transport material.

Requirements which the hole transport material should have include (1)having excellent hole transport ability, (2) being thermally stable andstable in the amorphous state, (3) being capable of forming a thin film,(4) being electrically and chemically stable, and (5) not beingdecomposed at the time of vapor deposition.

In order to achieve the above-mentioned objects, the present inventorsvariously manufactured EL elements by way of trial, and extensivelyevaluated newly synthesized hole transport materials, thereby leading tothe completion of the invention.

That is, the invention relates to a tetramine compound represented bythe following general formula (1):

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4.

Further, the invention relates to an organic EL element materialrepresented by the following general formula (1):

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4.

Furthermore, the invention relates to an organic EL element containing atetramine compound represented by the following general formula (1):

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4.

Moreover, the invention is a method for producing a tetramine compoundrepresented by general formula (1) shown below, which comprises the stepof conducting condensation reaction of a triphenyldiaminobiphenylcompound represented by the below-shown general formula (A) and adihalogen compound represented by the below-shown general formula (B):

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms;

wherein X represents a halogen atom, and n represents 3 or 4;

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4.

As another method, the invention also provides a method for producing atetramine compound represented by general formula (2) shown below, whichcomprises conducting condensation reaction of a diamino compoundrepresented by the below-shown general formula (C) and a halogencompound represented by the below-shown general formula (D), hydrolyzinga condensation product, and then, further conducting condensationreaction with a halogen compound represented by the below-shown generalformula (E):

wherein R4 represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted aryl group, and n represents 3 or 4;

wherein R1 represents a hydrogen atom, a tertiary alkyl group having 4to 8 carbon atoms, an unsubstituted aryl group or an aryl groupsubstituted with a tertiary alkyl group having 4 to 8 carbon atoms, R5represents a substituted or unsubstituted alkyl group or a substitutedor unsubstituted aryl group, and X represents a halogen atom;

wherein R2 represents a hydrogen atom, a tertiary alkyl group having 4to 8 carbon atoms, an unsubstituted aryl group or an aryl groupsubstituted with a tertiary alkyl group having 4 to 8 carbon atoms, andX represents a halogen atom;

wherein R1 and R2, which may be the same or different, each represents ahydrogen atom, a tertiary alkyl group having 4 to 8 carbon atoms, anunsubstituted aryl group or an aryl group substituted with a tertiaryalkyl group having 4 to 8 carbon atoms, and n represents 3 or 4.

In the invention, the hole transport material as described above isused. As a result, it not only has excellent hole transport ability, butalso forms a good thin film, and further, it is thermally stable.Compared to the case where a conventional hole transport material hasbeen used, the life under high temperature environment has beensignificantly improved. As a result, it has become clear that theorganic EL element having excellent luminous stability can be realized.

As described above, the invention is the organic EL element using thetetramine compound connected through a plurality of phenyl groups as thematerial for the hole transport layer, and by using the material of theinvention, luminous stability at the time of high temperature drivingwhich has been the largest problem of the conventional organic ELelement can be markedly improved, making it possible to markedly expandthe use range of the organic EL element. For example, development toapplications under high temperature environment such as interiorillumination, organic semiconductor lasers and in-vehicle applicationswhich require high durability has also become possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing typical EL element constitution;

FIG. 2 is an IR chart of HTM-1;

FIG. 3 is an IR chart of HTM-2;

FIG. 4 is an IR chart of HTM-3;

FIG. 5 is an IR chart of HTM-4;

FIG. 6 is an IR chart of HTM-5;

FIG. 7 is an IR chart of HTM-6;

As for reference numerals in the figure, 1 denotes a glass substrate, 2denotes a transparent anode, 3 denotes a hole injection layer, 4 denotesa hole transport layer, 5 denotes a layer used both as an electrontransport layer and as a light emitting layer, 6 denotes a buffer layer,and 7 denotes a cathode.

BEST MODE FOR CARRYING OUT THE INVENTION

The tetramine compound, the hole transport material of the invention, isa novel compound, and this can be synthesized by condensation reactionof a corresponding triphenyldiaminobiphenyl compound and a dihalogencompound, or by hydrolyzing a product obtained by condensation reactionof an N,N′-diacyl form of a corresponding diamine compound and acorresponding N-(4′-halogenated biphenyl)-N-acylaniline compound, andthen, conducting condensation reaction with a corresponding halogenatedaryl compound. Such condensation reaction is a production method knownas the Ullman reaction.

Identification of these compounds was performed by NMR analysis,elemental analysis and IR analysis. Purification was performed bypurification according to column chromatography, adsorption purificationaccording to an adsorbent, or recrystallization or crystallizationaccording to a solvent to a purity of 99.8% or more. Confirmation of thepurity was performed by high speed liquid chromatography or a TLCscanner. As physical property values, there were performed DSCmeasurement (Tg), TG-DTA measurement (decomposition point) and meltingpoint measurement. The melting point and decomposition point act as anindex of the heat stability of the hole transport layer, and the glasstransition point (Tg) acts as an index of the stability of the glassstate.

For the glass transition point (Tg), 5 mg of a sample powder was weighedinto an aluminum press cell, set to a DSC apparatus manufactured by SHIwhile allowing nitrogen gas to flow at 150 ml/min, elevated intemperature up to 400° C. at a rate of 10° C. per minute to melt thesample, then, cooled to −50° C. at a rate of −40° C. per minute, andelevated in temperature again up to 350° C. at a rate of 10° C. perminute. The glass transition point (Tg) was determined from anendothermic change at that time. For the decomposition point, 5 mg of asample powder was weighed into a platinum cell, set to a TG-DTAapparatus manufactured by SHI while allowing nitrogen gas to flow at 150ml/min, and elevated in temperature up to 800° C. at a rate of 10° C.per minute. From the resulting chart, a temperature at which a rapiddecrease in amount started was taken as the decomposition temperature.For the melting point, a tube bottom of a melting point measuring tubeME-18552 manufactured by Mettler was filled with a sample powder to alength of 10 mm, and elevated in temperature at 1° C. per minute using amelting point measuring device FP-62 manufactured by Mettler. Theresulting value was taken as the melting point.

The present inventors synthesized materials, variously changingsubstituent groups of compounds. As a result, the magnitudes of themelting point, decomposition point and glass transition point varydepending on the substituent group, and in the case of some substituentgroups, materials which are high in melting point, decomposition pointand glass transition point (Tg) could be obtained. Specific compoundexamples are shown in Tables 1-1 and 1-2. Further, some typicalsynthesis examples are shown as examples, but the invention should notbe construed as being limited to these compounds.

TABLE 1-1

HTM-1

HTM-2

HTM-3

HTM-4

HTM-5

HTM-6

HTM-7

HTM-8

TABLE 1-2

HTM-9

HTM-10

HTM-11

HTM-12

HTM-13

HTM-14

HTM-15

HTM-16

The tetramine compound represented by general formula (1), which wasconnected through three or four phenyl groups, had a high glasstransition point (Tg), and gave a good improving effect on the elementlife at the time of high temperature driving. Further, in a materialinto which an unsubstituted aryl group was introduced, a furthereffective effect was confirmed.

The organic EL element structures of the invention include onecomprising an anode, a hole transport layer, a light emitting layer, anelectron transport layer and a cathode laminated sequentially on asubstrate, or one comprising an anode, a hole transport layer, anelectron transport layer and a cathode laminated sequentially on asubstrate, wherein either the hole transport layer or the electrontransport layer has a light emitting function (serving as a lightemitting layer). Further, they include one comprising an ITO electrode,a hole injection layer, a hole transport layer, a light emitting layer,an electron transport layer, a cathode buffer layer and an aluminumelectrode.

Further, as the hole transport material according to the invention, onlyone kind of the tetramine compound represented by general formula (1)can be used. Alternatively, two or more kinds can be used in a mixedstate by forming a film by co-deposition or the like. Furthermore, thehole transport material of the invention can be used by co-depositionwith TPAC (1,1-bis[4-[N,N-di(p-tolyl)amino]]cyclohexane) or TPD(N,N′-diphenyl-N,N′-di(m-tolyl)benzidine) which is a conventional holetransport material. By using two or more kinds by co-deposition,crystallization thereof can be made difficult to occur in some cases.Moreover, the hole transport layer of the invention may serve as a lightemitting layer. Specifically, by combining the hole transport materialand an electron transport material having high hole blocking properties,the hole transport layer can be used as a light emitting layer.

Further, the electron transport layer of the invention may serve as alight emitting layer. For the layer of both the electron transport andthe light emission according to the invention, there can be used variousrare earth complexes, oxazole derivatives, polyparaphenylenevinylenesand the like as materials for the light emitting layer, as well asalumiquinoline trimers.

Furthermore, the higher performance EL element can be prepared by addinga light emitting material called a dopant, such as quinacridone,coumarin or rubrene, to the light emitting layer.

For the hole injection layer, copper phthalocyanine is used. For thecathode buffer layer, lithium fluoride is used.

EXAMPLES

The present invention will be illustrated in greater detail withreference to the following examples, but the invention should not beconstrued as being limited to these examples.

Synthesis of Hole Transport Materials Example 1 Synthesis of HTM-1

There were mixed 20.3 g (0.15 mole) of acetanilide, 73.1 g (0.18 mole)of 4,4′-diiodobiphenyl, 22.1 g (0.16 mole) of anhydrous potassiumcarbonate, 2.16 g (0.034 mole) of copper powder and 35 ml of n-dodecane,followed by reaction at 190 to 205° C. for 10 hours. The reactionproduct was extracted with 200 ml of toluene, and the insoluble matterwas removed by filtration. Then, the filtrate was concentrated todryness. The resulting solid matter was purified by columnchromatography (carrier: silica gel, eluate: toluene/ethyl acetate=6/1)to obtain 40.2 g (yield: 64.8%) of N-(4′-iodobiphenylyl)acetanilide. Themelting point was 135.0 to 136.0° C.

There were mixed 13.2 g (0.032 mole) ofN-(4′-iodobiphenylyl)acetanilide, 6.60 g (0.039 mole) ofN,N-di-phenylamine, 5.53 g (0.040 mole) of anhydrous potassiumcarbonate, 0.45 g (0.007 mole) of copper powder and 10 ml of n-dodecane,followed by reaction at 200 to 212° C. for 15 hours. The reactionproduct was extracted with 100 ml of toluene, and the insoluble matterwas removed by filtration. Then, the filtrate was concentrated to obtainoily matter. The oily matter was dissolved in 60 ml of isoamyl alcohol,and 1 ml of water and 2.64 g (0.040 mole) of 85% potassium hydroxidewere added, followed by hydrolysis at 130° C. After isoamyl alcohol wasremoved by steam distillation, extraction with 250 ml of toluene wasperformed, followed by washing with water, drying and concentration. Theconcentrate was purified by column chromatography (carrier: silica gel,eluate: toluene/n-hexane=1/2) to obtain 10.5 g (yield: 72.2%) ofN,N,N′-triphenyl-4,4′-diaminobiphenyl. The melting point was 167.5 to168.5° C.

There were mixed 8.80 g (0.021 mole) ofN,N,N′-triphenyl-4,4′-diaminobiphenyl, 5.00 g (0.01 mole) of4,4″-diiodo-p-terphenyl, 3.90 g (0.028 mole) of anhydrous potassiumcarbonate, 0.32 g (0.005 mole) of copper powder, 0.30 g (0.03 mole) ofsodium bisulfite and 10 ml of n-dodecane, followed by reaction at 195 to210° C. for 30 hours. The reaction product was extracted with 450 ml oftoluene, and the insoluble matter was removed by filtration. Then, thefiltrate was concentrated. To the concentrated solution, 60 ml ofmethanol was added to perform crystallization, and suction filtrationwas performed to obtain crude crystals. The crude crystals weredissolved in 50 ml of toluene under reflux, and allowed to cool down to45° C. Then, 100 ml of ethyl acetate was added dropwise to performcrystallization, thereby obtaining crystals.N,N′-bis(4-diphenylaminobiphenyl-4′-yl)-N,N′-diphenyl-4,4″-diamino-p-terphenylwas obtained in an amount of 5.73 g. The yield was 53.0%, and the HPLCpurity was 97.7%. The crystals were purified by column chromatography(carrier: silica gel, eluate: toluene/n-hexane=1/1) to obtain 4.75 g(HPLC purity: 100.0%, column purification yield: 84.8%) ofN,N′-bis(4-diphenylaminobiphenyl-4′-yl)-N,N′-diphenyl-4,4″-diamino-p-terphenyl.The melting point was 164.8° C. Identification of the product wasperformed by NMR analysis, elemental analysis and IR analysis. Theelemental analysis values are as follows: carbon; measured value; 88.92%(theoretical value; 89.11%), hydrogen; measured value; 5.78%(theoretical value; 5.56%), nitrogen; measured value; 5.07% (theoreticalvalue; 5.33%). The results of NMR analysis were as follows: 7.629 ppm(4H), 7.545-7.449 (12H), 7.313-6.987 ppm (42H).

Example 2 Synthesis of HTM-2

There were mixed 16.5 g (0.040 mole) ofN-(4′-iodobiphenylyl)acetanilide, 11.8 g (0.048 mole) ofN-(4-biphenyl)aniline, 8.3 g (0.060 mole) of anhydrous potassiumcarbonate, 0.1 g (0.002 mole) of copper powder and 10 ml of n-dodecane,followed by reaction at 200 to 212° C. for 15 hours. The reactionproduct was extracted with 200 ml of toluene, and the insoluble matterwas removed by filtration. Then, the filtrate was concentrated to obtainoily matter. The oily matter was dissolved in 60 ml of isoamyl alcohol,and 4 ml of water and 4.00 g (0.060 mole) of 85% potassium hydroxidewere added, followed by hydrolysis at 130° C. After isoamyl alcohol wasremoved by steam distillation, extraction with 250 ml of toluene wasperformed, followed by washing with water, drying and concentration. Theconcentrate was purified by column chromatography (carrier: silica gel,eluate: toluene/n-hexane=1/2) to obtain 15.2 g (yield: 77.8%, HPLCpurity: 97.0%) of N-(4-biphenylyl)-N,N′-diphenyl-4,4′-diaminobiphenyl.The melting point was 126.6 to 127.4° C.

There were mixed 11.08 g (0.022 mole) ofN-(4-biphenylyl)-N,N′-diphenyl-4,4′-diaminobiphenyl, 5.00 g (0.01 mole)of 4,4″-diiodo-p-terphenyl, 4.14 g (0.030 mole) of anhydrous potassiumcarbonate, 0.32 g (0.005 mole) of copper powder and 10 ml of n-dodecane,followed by reaction at 195 to 210° C. for 30 hours. The reactionproduct was extracted with 400 ml of toluene, and the insoluble matterwas removed by filtration. Then, the filtrate was concentrated. To theconcentrated solution, 60 ml of methanol was added to performcrystallization, and suction filtration was performed to obtain crudecrystals. The crude crystals were dissolved in 50 ml of toluene underreflux, and allowed to cool down to 45° C. Then, 100 ml of ethyl acetatewas added dropwise to perform crystallization, thereby obtainingcrystals.N,N′-bis[4-(4-biphenylylphenylamino)biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenylwas obtained in an amount of 7.91 g. The yield was 65.7%, and the HPLCpurity was 96.6%.

The crystals were purified by column chromatography (carrier: silicagel, eluate: toluene/n-hexane=1/1) to obtain 4.30 g (HPLC purity:100.0%, column purification yield: 56.3%) ofN,N′-bis[4-(4-biphenylylphenylamino)biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl.The melting point was 189.3° C. Identification of the product wasperformed by NMR analysis, elemental analysis and IR analysis. Theelemental analysis values are as follows: carbon; measured value; 89.98%(theoretical value; 89.82%), hydrogen; measured value; 5.61%(theoretical value; 5.53%), nitrogen; measured value; 4.35% (theoreticalvalue; 4.66%). The results of NMR analysis were as follows: 7.637 ppm(4H), 7.594-7.388 (24H), 7.328-7.160 ppm (34H), 7.073-7.025 ppm (4H).

Example 3 Synthesis of HTM-3

There were mixed 20.70 g (0.050 mole) ofN-(4′-iodobiphenylyl)acetanilide, 13.50 g (0.060 mole) of4-tert-butyldiphenylamine, 10.40 g (0.075 mole) of anhydrous potassiumcarbonate, 0.20 g (0.003 mole) of copper powder and 10 ml of n-dodecane,followed by reaction at 200 to 212° C. for 15 hours. The reactionproduct was extracted with 200 ml of toluene, and the insoluble matterwas removed by filtration. Then, the filtrate was concentrated to obtainoily matter. The oily matter was dissolved in 80 ml of isoamyl alcohol,and 5 ml of water and 5.00 g (0.075 mole) of 85% potassium hydroxidewere added, followed by hydrolysis at 130° C. After isoamyl alcohol wasremoved by steam distillation, extraction with 250 ml of toluene wasperformed, and the organic layer was washed with water, dried andconcentrated. The concentrate was purified by column chromatography(carrier: silica gel, eluate: toluene/n-hexane=1/2) to obtain 18.8 g(yield: 73.5%, HPLC purity: 98.0%) ofN-(4-tert-butylphenyl)-N,N′-diphenyl-4,4′-diaminobiphenyl. The meltingpoint was 125.6 to 126.6° C.

There were mixed 11.50 g (0.022 mole) ofN-(4-tert-butylphenyl)-N,N′-diphenyl-4,4′-diaminobiphenyl, 5.00 g (0.01mole) of 4,4″-diiodo-p-terphenyl, 4.14 g (0.030 mole) of anhydrouspotassium carbonate, 0.32 g (0.005 mole) of copper powder and 10 ml ofn-dodecane, followed by reaction at 195 to 210° C. for 30 hours. Thereaction product was extracted with 400 ml of toluene, and the insolublematter was removed by filtration. Then, the filtrate was concentrated.After the concentration, 60 ml of methanol was added to performcrystallization, and suction filtration was performed to obtain crudecrystals. The crude crystals were dissolved in 50 ml of toluene underreflux, and allowed to cool down to 45° C. Then, 100 ml of ethyl acetatewas added dropwise to perform crystallization, thereby obtainingcrystals.N,N′-bis[4-(4-tert-butyldiphenylamino)biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenylwas obtained in an amount of 6.70 g. The yield was 57.5%, and the HPLCpurity was 95.6%.

The crystals were purified by column chromatography (carrier: silicagel, eluate: toluene/n-hexane=1/2) to obtain 4.00 g (HPLC purity: 99.9%,column purification yield: 62.5%) ofN,N′-bis[4-(4-tert-butyldiphenylamino)biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl.The melting point was 209.5° C. Identification of the product wasperformed by NMR analysis, elemental analysis and IR analysis. Theelemental analysis values are as follows: carbon; measured value; 88.96%(theoretical value; 88.77%), hydrogen; measured value; 6.65%(theoretical value; 6.41%), nitrogen; measured value; 4.57% (theoreticalvalue; 4.82%). The results of NMR analysis were as follows: 7.629 ppm(4H), 7.545-7.425 (12H), 7.283-7.033 ppm (40H), 1.317 ppm (18H).

Example 4 Synthesis of HTM-4

There were mixed 8.10 g (0.019 mole) ofN,N,N′-triphenyl-4,4′-diaminobiphenyl, 4.00 g (0.008 mole) of4,4′″-diiodo-p-quaterphenyl, 3.90 g (0.028 mole) of anhydrous potassiumcarbonate, 0.32 g (0.005 mole) of copper powder, 0.30 g (0.03 mole) ofsodium bisulfite and 10 ml of n-dodecane, followed by reaction at 195 to210° C. for 30 hours. The reaction product was extracted with 450 ml oftoluene, and the insoluble matter was removed by filtration. Then, thefiltrate was concentrated. After the concentration, 60 ml of methanolwas added to perform crystallization, and suction filtration wasperformed to obtain crude crystals. The crude crystals were dissolved in50 ml of toluene under reflux, and allowed to cool down to 45° C. Then,100 ml of ethyl acetate was added dropwise to perform crystallization,thereby obtaining crystals.N,N′-bis(4-diphenylaminobiphenyl-4-yl)-N,N′-diphenyl-4,4′″-diamino-p-quaterphenylwas obtained in an amount of 5.08 g. The yield was 56.4%, and the HPLCpurity was 97.5%.

The crystals were purified by column chromatography (carrier: silicagel, eluate: toluene/n-hexane=2/3) to obtain 3.28 g (HPLC purity: 99.8%,column purification yield: 66.0%) ofN,N′-bis(4-diphenylaminobiphenyl-4-yl)-N,N′-diphenyl-4,4′″-diamino-p-quaterphenyl.The melting point was 173.1° C. Identification of the product wasperformed by NMR analysis, elemental analysis and IR analysis. Theelemental analysis values are as follows: carbon; measured value; 89.23%(theoretical value; 89.49%), hydrogen; measured value; 5.70%(theoretical value; 5.54%), nitrogen; measured value; 4.76% (theoreticalvalue; 4.97%). The results of NMR analysis were as follows: 7.719-7.639ppm (8H), 7.555-7.437 (12H), 7.319-6.989 ppm (42H).

Example 5 Synthesis of HTM-5

There were mixed 20.70 g (0.050 mole) ofN-(4′-iodobiphenylyl)acetanilide, 19.95 g (0.060 mole) ofN,N-bis(biphenyl-4-yl)amine, 10.40 g (0.075 mole) of anhydrous potassiumcarbonate, 0.20 g (0.003 mole) of copper powder and 10 ml of n-dodecane,followed by reaction at 200 to 212° C. for 15 hours. The reactionproduct was extracted with 200 ml of toluene, and the insoluble matterwas removed by filtration. Then, the filtrate was concentrated to obtaincrude crystals. The crude crystals were dissolved in 80 ml of isoamylalcohol, and 5 ml of water and 5.00 g (0.075 mole) of 85% potassiumhydroxide were added, followed by hydrolysis at 130° C. After isoamylalcohol was removed by steam distillation, extraction with 250 ml oftoluene was performed, and the organic layer was washed with water,dried and concentrated. The concentrate was purified by columnchromatography (carrier: silica gel, eluate: toluene/n-hexane=1/2) toobtain 24.2 g (yield: 69.9%, HPLC purity: 98.0%) ofN,N-bis(biphenyl-4-yl)-N′-phenyl-4,4′-diaminobiphenyl. The melting pointwas 145.8 to 146.0° C.

There were mixed 12.68 g (0.022 mole) ofN,N-bis(biphenyl-4-yl)-N′-phenyl-4,4′-diaminobiphenyl, 5.00 g (0.01mole) of 4,4″-diiodo-p-terphenyl, 4.14 g (0.030 mole) of anhydrouspotassium carbonate, 0.32 g (0.005 mole) of copper powder and 10 ml ofn-dodecane, followed by reaction at 195 to 210° C. for 30 hours. Thereaction product was extracted with 800 ml of toluene, and the insolublematter was removed by filtration. Then, the filtrate was concentrated.After the concentration, 100 ml of methanol was added to performcrystallization, and suction filtration was performed to obtain crudecrystals. The crude crystals were dissolved in 300 ml of toluene underreflux, and allowed to cool down to 45° C. Then, 300 ml of ethyl acetatewas added dropwise to perform crystallization, thereby obtainingcrystals.N,N′-bis[4-{bis(biphenyl-4-yl)amino}biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenylwas obtained in an amount of 9.43 g. The yield was 65.9%, and the HPLCpurity was 94.7%.

The crystals were purified by column chromatography (carrier: silicagel, eluate: toluene/n-hexane=1/2) to obtain 5.47 g (HPLC purity:100.0%, column purification yield: 61.3%) ofN,N′-bis[4-{bis(biphenyl-4-yl)amino}biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl.The melting point was 204.5° C. Identification of the product wasperformed by NMR analysis, elemental analysis and IR analysis. Theelemental analysis values are as follows: carbon; measured value; 90.22%(theoretical value; 90.37%), hydrogen; measured value; 5.73%(theoretical value; 5.50%), nitrogen; measured value; 4.05% (theoreticalvalue; 4.13%). The results of NMR analysis were as follows: 7.637-7.396ppm (40H), 7.336-7.172 (32H), 7.081-7.029 ppm (2H).

Example 6 Synthesis of HTM-6

There were mixed 20.70 g (0.050 mole) ofN-(4′-iodobiphenylyl)acetanilide, 16.88 g (0.060 mole) ofN,N-bis(4-tert-butylphenyl)amine, 10.40 g (0.075 mole) of anhydrouspotassium carbonate, 0.20 g (0.003 mole) of copper powder and 10 ml ofn-dodecane, followed by reaction at 200 to 212° C. for 15 hours. Thereaction product was extracted with 200 ml of toluene, and the insolublematter was removed by filtration. Then, the filtrate was concentrated toobtain oily matter. The oily matter was dissolved in 80 ml of isoamylalcohol, and 5 ml of water and 5.00 g (0.075 mole) of 85% potassiumhydroxide were added, followed by hydrolysis at 130° C. After isoamylalcohol was removed by steam distillation, extraction with 250 ml oftoluene was performed, and the organic layer was washed with water,dried and concentrated. The concentrate was purified by columnchromatography (carrier: silica gel, eluate: toluene/n-hexane=1/2) toobtain 20.21 g (yield: 75.5%, HPLC purity: 98.0%) ofN,N-bis(4-tert-butylphenyl)-N′-phenyl-4,4′-diaminobiphenyl. The meltingpoint was 161.1 to 162.0° C.

There were mixed 11.78 g (0.022 mole) ofN,N-bis(4-tert-butylphenyl)-N′-phenyl-4,4′-diaminobiphenyl, 5.00 g (0.01mole) of 4,4″-diiodo-p-terphenyl, 4.14 g (0.030 mole) of anhydrouspotassium carbonate, 0.32 g (0.005 mole) of copper powder and 10 ml ofn-dodecane, followed by reaction at 195 to 210° C. for 30 hours. Thereaction product was extracted with 400 ml of toluene, and the insolublematter was removed by filtration. Then, the filtrate was concentrated.After the concentration, 60 ml of methanol was added to performcrystallization, and suction filtration was performed to obtain crudecrystals. The crude crystals were dissolved in 50 ml of toluene underreflux, and allowed to cool down to 45° C. Then, 100 ml of ethyl acetatewas added dropwise to perform crystallization, thereby obtainingcrystals.N,N′-bis[{bis(4-tert-butylphenyl)amino}biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenylwas obtained in an amount of 8.22 g. The yield was 61.1%, and the HPLCpurity was 94.8%.

The crystals were purified by column chromatography (carrier: silicagel, eluate: toluene/n-hexane=1/2) to obtain 4.98 g (HPLC purity:100.0%, column purification yield: 60.6%) ofN,N′-bis[{bis(4-tert-butylphenyl)amino}biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl.The melting point was 215.0° C. Identification of the product wasperformed by NMR analysis, elemental analysis and IR analysis. Theelemental analysis values are as follows: carbon; measured value; 88.56%(theoretical value; 88.50%), hydrogen; measured value; 7.18%(theoretical value; 7.11%), nitrogen; measured value; 4.31% (theoreticalvalue; 4.39%). The results of NMR analysis were as follows: 7.623 ppm(4H), 7.538-7.407 (12H), 7.275-7.035 ppm (38H), 1.313 ppm (36H).

Then, the physical properties of the respective compounds synthesized inthe synthesis examples are collectively shown in Table 2.

TABLE 2 Decomposition HPLC Purity Tg Point Melting Point HTM-1 100.0%151.0° C. 561.2° C. 164.8° C. HTM-2 100.0% 154.5° C. 572.3° C. 189.3° C.HTM-3 99.9% 158.1° C. 530.7° C. 209.5° C. HTM-4 99.8% 156.5° C. 568.1°C. 173.1° C. HTM-5 100.0% 173.3° C. 504.5° C. 204.5° C. HTM-6 100.0%181.0° C. 524.1° C. 215.0° C.

Preparation of EL Elements and Characteristic Evaluation

In the following examples, the respective compounds synthesized in theabove-mentioned examples were actually evaluated as EL elements, and theluminous characteristic, the stability of the luminous characteristicand the storage stability of the elements were studied. As shown inTable 1, the EL element was prepared by vapor depositing a holeinjection layer 3, hole transport layer 4, a layer 5 used both as anelectron transport layer and as a light emitting layer, a cathode bufferlayer 6 and a cathode (aluminum electrode) 8 in this order on an ITOelectrode previously formed as a transparent anode 2 on a glasssubstrate 1. A surface of the glass substrate on which the ITO electrodehad been formed as a film was washed by UV & ozone treatment. This wasset in a vapor depositing apparatus. Subsequently, copperphthalocyanine, the hole transport material of the invention, a purifiedalumiquinoline trimer, lithium fluoride and aluminum, respectively, wereset in the vapor depositing apparatus, as the hole injection material,the hole transport material, the electron transportable light emittingmaterial, the buffer layer and the cathode. Monitoring the filmthickness with a crystal oscillator, the vapor deposition was performedat a vapor deposition speed of 2.00 angstroms/sec. The hole injectionlayer was 25 nm, the hole transport layer was 35 nm, the electrontransportable light emitting layer was 1 nm, and the cathode was vapordeposited at a vapor deposition speed of 4.00 angstroms/sec up to 150nm. These vapor depositions were all continuously performed withoutbraking vacuum. Immediately after the preparation of the element, theelectrode was taken out in dry nitrogen, and subsequently,characteristic measurement was carried out.

The luminous characteristic of the resulting element was defined by theluminous luminance at the time when a current of 100 mA/cm² was applied.Further, the luminous stability at the time of high temperature drivingwas compared using the element to which sealing treatment was notapplied so that the difference due to the film characteristics of thehole transport material could be directly compared. Under a hightemperature environment of 100° C., an initial voltage at which theelement showed a luminous luminance of 1000 cd/m² was applied to measurea decrease in luminous luminance and changes in current value.

Example 7

Using HTM-1 (R1, R2, R3=H, n=3, melting point=164.8° C., Tg=151.0° C.)as the hole transport material, an ITO electrode washed by UV & ozonetreatment, purified copper phthalocyanine as the hole injectionmaterial, a purified alumiquinoline trimer as the electron transportablelight emitting material, lithium fluoride as the buffer layer, andaluminum as the cathode were set in a vapor depositing apparatus.Monitoring the film thickness with a crystal oscillator, the vapordeposition was performed at a vapor deposition speed of 2.00angstroms/sec. The hole injection layer was 25 nm, the hole transportlayer was 35 nm, the electron transportable light emitting layer was 1nm, and the cathode was vapor deposited at a vapor deposition speed of4.00 angstroms/sec up to 150 nm. These vapor depositions were allcontinuously performed without braking vacuum. Immediately after thepreparation of the element, the electrode was taken out in dry nitrogen,adhered to a peltiert element, and heated to 100° C. Characteristicevaluation was conducted while keeping 100° C. The voltage at which aninitial luminance of 1000 cd/m² was shown was 6.0 V. This element showeda maximum luminance of 1099 cd/m² at 11.6 mA after stabilization.Thereafter, the luminance decreased to 462 cd/m2 after 5 hours, to 321cd/m2 after 8 hours, and to 214 cd/m2 after 12 hours. The drivingcurrent after 12 hours was 2.2 mA.

Comparative Example 1

For comparison, using a compound represented byN,N′-bis(naphthalene-1-yl)-N,N′-diphenylbenzidine (hereinafter α-NPD)which is the mainstream of the hole transport material at present, an ELelement was prepared under the same conditions as in Example 7, and thecharacteristic thereof was examined by a similar method. This elementshowed an initial luminous of 1000 cd/m² at 5.0 V. This element showed amaximum luminance of 1089 cd/m² at 10.6 mA after stabilization. Althoughthis element was lower in driving voltage than the element of Example 7,the luminous luminance showed 426 cd/m² after 5 hours, 282 cd/m² after 8hours, and 184 cd/m² after 12 hours, and larger decreases in luminancewere observed. Further, the driving current after 12 hours was 2.8 mA,which showed lower current efficiency than that of the element ofExample 7.

Example 8

In a manner similar to Example 7, there were prepared EL elements usingHTM-2 (R1=phenyl group, R2, R3=H, n=3, melting point=189.3° C.,Tg=154.5° C.), HTM-3 (R1=tert-butyl group, R2, R3=H, n=3, meltingpoint=200.5° C., Tg=158.1° C.), HTM-4 (R1, R2, R3=H, n=4, meltingpoint=173.1° C., Tg=156.5° C.), HTM-5 (R1, R2=phenyl group, R3=H, n=3,melting point=204.5° C., Tg=173.3° C.) and HTM-6 (R1,R2=4-tert-butylphenyl group, R3=H, n=3, melting point=215.0° C.,Tg=181.0° C.), respectively, as the hole transport materials, and thecharacteristic thereof was evaluated. The results thereof are shown inTable 3. All the substitution positions of R1 and R2 in tetraminecompounds HTM-1 to HTM-6 each connected through the above-mentionedplurality of phenyl groups are the p-position.

TABLE 3 Luminous Characteristic/cd · m⁻² HTM-1 5300 HTM-2 5500 HTM-35500 HTM-4 5300 HTM-5 5400 HTM-6 5450

Example 9

In the element prepared in Example 8, changes in a external appearanceof the element at the time when it was stored under a high temperatureof 100° C. were observed. The results thereof are shown in Table 4.

For α-NPD, the element became clouded by storage for 24 hours. Incontrast, all the compounds synthesized in the invention kepttransparency to show excellent amorphous film stability under hightemperature environment.

TABLE 4 After 24 Hours After 100 Hours α-NPD X X HTM-1 ◯ ◯ HTM-2 ◯ ◯HTM-3 ◯ ◯ HTM-4 ◯ ◯ HTM-5 ◯ ◯ HTM-6 ◯ ◯ X: Clouded, ◯: Not clouded

From the above, it is revealed that the elements synthesized in theinvention, which are prepared using as the hole transport materials thetetramine compounds each connected through the plurality of phenylgroups, are excellent in heat stability.

Although the invention has been described in detail with reference tospecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention.

The present application is based on Japanese Patent Application No.2003-434432 filed on Dec. 26, 2003, the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The material of the invention is suitable as a material for an organicEL element requiring luminous stability at the time of high temperaturedriving which has been the largest problem of the conventional organicEL element.

1. A method for producing a tetramine compound represented by formula(1) shown below, comprising: condensation reacting atriphenyldiaminobiphenyl compound represented by formula (A) and adihalogen compound represented by formula (B):

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4;

wherein X represents a halogen atom, and n represents 3 or 4;

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4.
 2. A method for producing a tetramine compound represented by formula(2) shown below, comprising: a first condensation reacting of a diaminocompound represented by formula (C) and a halogen compound representedby formula (D) to form a condensation product; hydrolyzing thecondensation product; and a second condensation reacting with a halogencompound represented by formula (E):

wherein R4 represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted aryl group, and n represents 3 or 4;

wherein R1 represents a hydrogen atom, a tertiary alkyl group having 4to 8 carbon atoms, an unsubstituted aryl group or an aryl groupsubstituted with a tertiary alkyl group having 4 to 8 carbon atoms, R5represents a substituted or unsubstituted alkyl group or a substitutedor unsubstituted aryl group, and X represents a halogen atom;

wherein R2 represents a hydrogen atom, a tertiary alkyl group having 4to 8 carbon atoms, an unsubstituted aryl group or an aryl groupsubstituted with a tertiary alkyl group having 4 to 8 carbon atoms, andX represents a halogen atom;

wherein R1 and R2, which may be the same or different, each represents ahydrogen atom, a tertiary alkyl group having 4 to 8 carbon atoms, anunsubstituted aryl group or an aryl group substituted with a tertiaryalkyl group having 4 to 8 carbon atoms, and n represents 3 or
 4. 3. Themethod for producing a tetramine compound according to claim 1, whereinthe triphenyldiaminobiphenyl compound is selected from the groupconsisting of: N,N,N′-triphenyl-4,4′-diaminobiphenyl;N-(4-biphenylyl)-N,N′-diphenyl-4,4′-diaminobiphenyl;N-(4-tert-butylphenyl)-N,N′-diphenyl-4,4′-diaminobiphenyl;N,N,N′-triphenyl-4,4′-diaminobiphenyl;N,N-bis(biphenyl-4-yl)-N′-phenyl-4,4′-diaminobiphenyl; andN,N-bis(4-tert-butylphenyl)-N′-phenyl-4,4′-diaminobiphenyl.
 4. Themethod for producing a tetramine compound according to claim 1, whereinthe dihalogen compound is 4,4″-diiodo-p-terphenyl or4,4′″-diiodo-p-quaterphenyl.
 5. The method for producing a tetraminecompound according to claim 1, wherein the tetramine compound is atleast one selected from the group consisting of:N,N′-bis(4-diphenylaminobiphenyl-4′-yl)-N,N′-diphenyl-4,4″-diamino-p-terphenyl;N,N′-bis[4-(4-biphenylylphenylamino)biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl;N,N′-bis[4-(4-tert-butyldiphenylamino)biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl;N,N′-bis(4-diphenylaminobiphenyl-4-yl)-N,N′-diphenyl-4,4′″-diamino-p-quaterphenyl;N,N′-bis[4-{bis(biphenyl-4-yl)amino}biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl;andN,N′-bis[{bis(4-tert-butylphenyl)amino}biphenyl-4′-yl]-N,N′-diphenyl-4,4″-diamino-p-terphenyl.6. The method for producing a tetramine compound according to claim 1,wherein said condensation reacting is performed at a range of from 195to 210° C.
 7. The method for producing a tetramine compound according toclaim 1, wherein said condensation reacting is performed for from 25 to35 hours.
 8. The method for producing a tetramine compound according toclaim 1, wherein the molar ratio of the triphenyldiaminobiphenylcompound to the dihalogen compound is from 1:1 to 4:1.
 9. The method forproducing a tetramine compound according to claim 1, wherein the molarratio of the triphenyldiaminobiphenyl compound to the dihalogen compoundis from 2:1 to 3:1.
 10. The method for producing a tetramine compoundaccording to claim 1, further comprising connecting said tetraminecompound through at least one phenyl group to at least one identicaltetramine compound.
 11. The method for producing a tetramine compoundaccording to claim 10, wherein said tetramine compound is connectedthrough three or four phenyl groups to the at least one identicaltetramine compound.
 12. The method for producing a tetramine compoundaccording to claim 1, further comprising connecting said tetraminecompound through at least one phenyl group to at least one differenttetramine compound according to formula (1)

wherein R1, R2 and R3, which may be the same or different, eachrepresents a hydrogen atom, a tertiary alkyl group having 4 to 8 carbonatoms, an unsubstituted aryl group or an aryl group substituted with atertiary alkyl group having 4 to 8 carbon atoms, and n represents 3 or4.
 13. The method for producing a tetramine compound according to claim12, wherein said tetramine compound is connected through three or fourphenyl groups to the at least one different tetramine compound.
 14. Themethod for producing a tetramine compound according to claim 10, whereinsaid tetramine compound, connected through at least one phenyl group toat least one identical tetramine compound, is in the form of a film. 15.The method for producing a tetramine compound according to claim 12,wherein said tetramine compound, connected through at least one phenylgroup to at least one different tetramine compound, is in the form of afilm.